We review the best CPU coolers on the market

High-end processors are painfully pricey. That makes us grumpy. Even if you could afford to unload £800 on a CPU, we'd therefore prefer it if you didn't. It only encourages Intel to pile on the pounds.

But there is hope, and it comes in the form of improved cooling. Often, the only significant difference between chips priced hundreds of pounds apart is clockspeed. Even with the most basic of cooling, it's often possible to close, or even entirely leapfrog that frequency, and therefore performance gap, but bolt on a better cooling solution and things get really interesting.

A critical factor is the price of cooling solutions. £50 here or there isn't very much when it comes to processor pricing, but it buys you one hell of an air cooler.

While water cooling options tend to be a bit more expensive, even £100 or so for one is mundane money compared to a high-end processor. What's more, CPU coolers have much longer legs than the chips themselves. Six months is sometimes enough for a CPU to transmogrify from shiny to shonky. After a couple of years, you're often struggling to keep up with the latest applications.

But not coolers. Generally, a good cooler today is a good cooler tomorrow. It's as solid an investment as you get with PC kit. The knock-on effect of squeezing more performance from your processor is that it should last a bit longer before an upgrade is critical.

If that isn't enough, there are a few fringe benefits to boot. Running your CPU at any given clockspeed usually means it will be more reliable. Failures are pretty rare, but instability due to heat isn't. Counter intuitively, upgraded cooling is often quieter, too. In fact, sometimes it's silent.

Stick all that together and give it a good stir and you have a winning mix and one of the most cost effective ways to perk up your PC's performance. With all the weird and wonderful cooling designs out there, it's also a lot of fun.

Overclocking ain't what it used to be. Whether that's for good or ill depends on the moment in history you choose for a yardstick. It wasn't all that long ago that it was not only possible, but terrifyingly easy to fry a CPU via an ill-advised overclocking escapade. And remember when overclocking involved shorting circuits by drawing on the chip package with a pencil? Seriously shonky stuff.

These days, it's hard, bordering on impossible, to irreversibly nuke a CPU. You have to do something very, very stupid. In fact, leave the voltages alone and you'll struggle to do lasting damage. So overclocking is a hell of a lot less scary than it used to be. Cue much rejoicing.

But there have also been changes that make it much harder to turn budget chips into giant-killers. Firstly, the CPU market is much more tiered than it used to be. Back in the days of those pencil hacks, the only difference between a high-end monster and a more mundane model was clockspeed.

Today, top chips are often based on different silicon from their bargain basement brethren; more cores, extra features, a different socket and all that jazz. But that's not the only change. Particularly when it comes to Intel processors, overclocking opportunities are very carefully controlled.

Since the introduction of the Sandy Bridge generation of processors, overclocking has been essentially limited to the CPU multiplier. On the one hand, that's great because multiplier overclocks are the cleanest and the quickest. You don't have to worry about the knock-on effects on other sub-systems like memory or the PCI Express bus.

On the other, they're not much use if the multiplier is locked. And locked it largely is on most Intel chips.

Bang for your buck

You have to pay extra for either a K series or an Extreme model to get access to fully unlocked multipliers. It's all very frustrating, but that's what happens when a single vendor dominates the market. Yes, AMD offers fully unlocked chips for much less money, but they're typically lower performing and don't overclock as well.

For that reason, we've based this month's cooling spectacular of our favourite CPU of recent years, the Intel Core i5-2500K. It's not the fastest chip in all areas. Its lack of HyperThreading holds things back a little when it comes to uber-threaded software like video encoding. It's also been recently superseded by the new Ivy Bridge generation and in particular the Core i5-3570K.

But it's still an absolute beast when it comes to games, which are not only our favourite thing to do with PCs, but also just so happen to be the app type that benefits most from performance upgrades. Oh, and the 2500K is also a great overclocker, so it should help sort the high-falutin heat sinks from the clunky coolers.

Despite recent limitations on overclocking, then, there are still opportunities for modders to extract massive performance gains with a good cooler. If we've sold you on the general idea of a cooling upgrade, let's deep dive into the specifics.

Air versus water, that's the classic contest. The most obvious things air-cooling has going for it is cost and complexity. It's generally pretty cheap and almost always simple. In fact given that some air coolers have no moving parts, you couldn't get any simpler. Long term reliability, then, isn't much of an issue.

That's more than you can say for water coolers. At least, that used to be the case with the typically rather Heath Robinson affairs that used to pass for water coolers. The funky blue liquids and clear piping were fun, but they often made for an unreliable system that needed fairly regular fettling - or worse, a terminal leak onto a critical component. Yikes.

Water-tight

Such kits were also far from user friendly in terms of initial set up and installation. Fortunately, little to none of that applies to modern so-called enclosed water cooling solutions. You pretty much pull them out of the box, plug 'em in and crank up the clocks.

Okay, they do come with large radiator assemblies, which make the installation procedure a little less routine, but then fancy air coolers can be a right pain in the parallel port, too. Modern water coolers are also usually meant to be zero maintenance, which means price is the major downside to liquid cooling.

It ain't cheap. The upside, at least in theory, is improved cooling. Funnily enough, though, the principles for both water and air-cooling are essentially the same. In both cases, a block of metal sits atop the CPU and transmits heat to a cooling array via a medium, which, in turn, is cooled by air, either ambiently for a passive cooler or actively with fans.

In the case of so-called air coolers, it's actually heat being conducted through metal. With a water cooler, it's liquid being pumped around the system. So, the choice is really metal versus water cooling.

One thing you generally don't have to worry about, however, is socket compatibility. Most cooling kits are designed to play nicely with existing CPU sockets. AMD's socket has been essentially static when it comes to cooling attachments for years. Meanwhile, most kits will support sockets as old as LGA 775 for Intel kit, which we reckon covers just about everyone, but it's easy enough to check the specs.

That said, you should have a think about compatibility with your current PC case and motherboard, as well as your graphics setup. There are lots of variables to bear in mind here, so it's difficult to come up with simple prescriptions, but you need to generally be aware of the space inside you case and also consider that some of the more extreme coolers can foul the PCI Express slot nearest the CPU socket. If you've got a board with just one such slot, that can rule out certain coolers.